The present invention relates in general to interfacing a shared output transducer to an audio program source and a telephone, and more specifically to coordinating operation of an audio system and a cellular phone in a vehicle.
Increasing numbers of automotive vehicles are being equipped with mobile communication devices, such as cellular telephones. Nearly every vehicle is equipped with an audio system; such as, a radio, a cassette tape, a CD player, and combinations thereof. Consequently, the operation of each system take into account the presence of the other system. For example, it is desirable for the audio system to inhibit its production of sound during times when a call is in progress on the cellular phone. However, an unexpected and abrupt cutting off of the audio system upon the receipt of an incoming call is undesirable, especially if the audio output was being played at a loud volume.
In order to improve the convenience of using a mobile communications system, a transceiver is preferably provided having hands-free operation wherein the user of the system is not required to hold a handset. Instead, a microphone is located near the user in order to pick up voice signals, and a loudspeaker mounted in the vehicle is employed to project audible signals to be heard by the user.
It would be desirable to integrate the two systems together in order to share components and to thereby eliminate duplication and reduce costs and complexity of the overall system. Thus, automotive vehicles are known that contain a cellular phone and an audio system that share a common speaker. Input to the shared speaker has been controlled by a switching relay. However, relays cause abrupt cut-offs in the audio program material Furthermore, undesirable noises (e.g., "pops") are created by switching of the relay and by turning on and off of the audio system and the cellular phone.
Theses are some of the disadvantages of the prior art that the present invention overcomes.